saros cycle -- from Greiner's book Hi, I'm having some trouble about the calculation of saros cycle in example 13.9 of Greiner's book "classical mechanics: system of particles and hamiltonian dynamics". I am confused about the factor "3" of eqn. (13.35). This equation is derived from (13.27). However as I did it, I only got a factor "2". Obviously the factor "3" is necessary for the final answer to be close to the true value. However I can't figure out how this factor comes. (I've no idea whether this could be posted here. This is neither a homework nor a problem in the course I'm taking.) It will really be very much appreciated if you can give me some help. Thanks.